Abstract

An extensive measurement campaign was carried out at the von Karman Institute for Fluid Dynamics to assess the aerodynamic performance of an ultra-low aspect ratio centripetal turbine stator. The test section consisted of 18 periodic sectors of two blade passages each, tested at transonic conditions in a blow-down facility. Particle image velocimetry (2D-PIV) measurements were performed in the trailing edge area at blade midheight. Further downstream, 16 micro virtual 3-hole pressure probes were used to measure the aerodynamic performance at about 44% of the radial chord, downstream of the trailing edge. Results describe a highly swirling flow-field characterized by a very large tangential velocity component increasing at smaller radii. The radial component decreased instead to compensate for an opening of the test section closer to its center, enhancing therefore the tangential nature of the generated flow field. Adjacent blades showed asymmetric wakes as an effect of the particular design of the nozzle. The performance analysis exhibited very high loss coefficients (always higher than 12%) which have to be related to the extremely small aspect ratio of the cascade.